Diagnostic instruments having viewing optics for viewing a target are commonly known, particularly in the medical field, for conducting diagnostic examinations. An example is a colposcope which is used by gynecologists to conduct patient vaginal examinations. Typically, the scope is placed a predetermined distance from the patient and pointed at a speculum, which is used to hold open the vaginal cavity in order to allow viewing of the cervix. Light from an illumination source of the colposcope is projected along an illumination axis with the illumination system being set at an angle off-axis relative to an optical viewing system, such as shown in FIG. 2.
A recurring problem is that the presence of the speculum, as well as the off-axis alignment of the illumination system causes shadowing of the image being viewed,(ie: the cervix or other intended target), making examination difficult, as well as time-consuming to perform. In the same described procedure, shadowing of the viewed image may also occur when a physician attempts to obtain a culture, or otherwise introduces a probe or swab into the vaginal cavity.
There is a need, therefore, to provide an improved illumination system, particularly for a colposcope, but advantageously for other diagnostic instruments as well, which reduces the effects of shadowing and allows more efficient use of the instrument's optical system.